79 F-150 4X4 Distirbutor issues
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Junior User
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79 F-150 4X4 Distirbutor issues
Been awhile since I have been on here but, can use some advice. My 79 F-150 4X4 has a 400 and has recently been giving some distributor problems. Initially, it fired up drove two feet, lurched forward and died. Troubleshot it down to the gear roll pin sheared. Pulled the distributor and replaced the roll pin, reinstalled the distributor and finally got it to stay running. The problem is won't time right. I have it set to 10 BTDC right now and if I turn the distributor just the slightest in either direction it dies. Took it for a drive and it is real sluggish and backfiring through the carb. Also it will buck forward every now and then. The bucking feels just like every time the distributor has gone out on me. I have checked all vacuum lines and adjusted idle mixture and nothing seems to get it right. I am leaning towards replacing the distributor, thinking possibly the roll pin is allowing the gear to travel, which would explain the bucking. Any thoughts or advice would be appreciated. Sorry so long, just trying to be thorough. 
Lead Driver
Joined: Jul 2017
Posts: 9,603
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From: San Jose, CA
Is this a standard Duraspark distributor? Normally when it dies from slightly turning I'd suspect a bad points plate or wire. But since these are pretty reliable in that area, and have three wires, it's not as common.
I wonder if the pickup coil and wires are in fact failing anyway?
They're relatively easy and inexpensive to replace by themselves, but if this is an original distributor (sounds like not?) then it's probably pretty worn out in the rest of the parts and should be replaced entirely.
What about the advance mechanism? When you check timing is it bouncing around at all? The timing chains stretch on these things pretty badly, which would make it bounce but not likely die. Erratic timing is not great, but it still usually runs.
Sorry I don't have any direct cures. Sounds like you know your way around a distributor swap though. Still, I'd check the physical mechanism. Strange that it sheared a pin after all this time, if it's an older unit.
How old is this one by the way?
Paul
I wonder if the pickup coil and wires are in fact failing anyway?
They're relatively easy and inexpensive to replace by themselves, but if this is an original distributor (sounds like not?) then it's probably pretty worn out in the rest of the parts and should be replaced entirely.
What about the advance mechanism? When you check timing is it bouncing around at all? The timing chains stretch on these things pretty badly, which would make it bounce but not likely die. Erratic timing is not great, but it still usually runs.
Sorry I don't have any direct cures. Sounds like you know your way around a distributor swap though. Still, I'd check the physical mechanism. Strange that it sheared a pin after all this time, if it's an older unit.
How old is this one by the way?
Paul
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Junior User
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Paul,
Timing seems to be holding steady when I put a light on it. The distributor is about 1 year and 1/2 old. It was an autozone replacement. The pickup coil checks out when I put the ohm meter to it. Thanks for your input.
Timing seems to be holding steady when I put a light on it. The distributor is about 1 year and 1/2 old. It was an autozone replacement. The pickup coil checks out when I put the ohm meter to it. Thanks for your input.
Fleet Mechanic
Joined: Jul 2017
Posts: 1,276
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From: KY
Well if its just a 1 yr an 1/2 old and sheared that pin I would replace distributor with something maybe better than autozone supplies . Past experience on ignition parts from autozone are cheap china crap. On my 72 challenger I converted to a HEI GM 4 Pin Module as the electronic ignition new parts bad out of box tried 3 or 4 an gave up . Your distributor is probably poorly made from autozone, just my opinion
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